This invention relates to a new and improved die-drawing and/or extruding device, primarily for converting flat metal and composite stock into formed slit tubing which may be subsequently welded to form a tube having seamless characteristics. In addition, flat stock tubes or solid stock can be formed either with a tapered, spiralled, ribbed or uniform shape, and depending on the shape of the dies, the formed work piece can assume a variety of shapes such as circular, hexagonal, square, triangular, D-section, rectangular, I-beam, etc., with combinations of the above, and transitional areas therebetween.
While the use of flat metal represents one form of feedstock, ready made tubes can also be processed for purposes of size reduction as a uniform shape, or in a tapered form, either step tapered, reverse tapered, as a venturi shape, as a continuous stream of pre-defined shapes, etc.
In addition, solids, laminates, plastic-coated metals, and composites, all in various cross sectional shapes may be formed or modified by the process of this invention.
Many prior art patents disclose the general process of drawing flat stock, tubes, rods and the like through rotating dies, rolling mills, and so forth. Typical publications in this field are U.S. Pat. Nos. 433,580; 860,879; 989,508; 1,178,812; 1,200,304; 1,455,652; 1,652,396; 1,700,508; 2,780,948; 3,274,816; 3,452,424; 3,650,138; 3,895,510; 3,938,724; and, 4,578,985.
Prior art patents of the inventor herein include: U.S. Pat. Nos. 3,327,513; 3,564,884; 3,585,832; 3,593,559; 3,596,491; 3,605,476; and, 3,540,259.
Some disadvantages posed by these prior art patents are that the feedstock is subject to a crushing action, and this can produce galling, embrittlement and stress cracking of the material. While subsequent straightening, annealing and cleaning operations may be employed to relieve some of these defects, they involve extra, expensive steps, and reduce the aesthetic appearance of the product. Furthermore, the prior art requires a series of intermediate operations preparatory to final sizing and shaping.
An object of this invention is to provide a new and improved drawing and/or etrusion device and process, primarily for drawing and/or extruding flatstock, tubes, solids, and the like to produce a constant size, uniform, or concave or convex tapered product having improved strength characteristics, and fewer structural and surface imperfections.
A further object of this invention is to form tubular products such as laminates, plastic feedstock, tubes and rods, plastic covered metal, multiple tubes from two or more flatstock sheets, and so forth.
A further object is to eliminate the requirement of swaging and/or pointing operation prior to drawing.
Another object is to form an incomplete tube employing the drawing apparatus of this invention which can then be readily welded.